This invention relates to minimally medical devices, more particularly, wire guides and related devices.
It has been recognized that the placement of a series of markings on a surgical instrument such as a wire guide, catheter, needle, etc., can aid the physician in proper placement of the device in the body of a patient during a medical procedure. These markings can include bands, dots, lettering, numbering, colors, or other types of indicia to indicate position or movement of the device within the body. Visually distinguishable marks are often located at regular predetermined intervals, e.g., placement of one dot or band at the 5 cm mark, two dots or bands at 10 cm, etc. Such a system of indicia can be made to be visible under fluoroscopy by the use of certain radiopaque metals, or compounds incorporated into or printed on the device. When direct visualization is possible, numerical values imprinted on the device can be used as a scale for measuring structures or distance.
The ability to quantify distances or make measurements is the primary benefit that has inspired the development of marker systems for wire guides, catheters, and the like. Another use of markings is to provide a system whereby the clinician can determine relative movement of the device within the body. This has also been found to be useful in endoscopic procedures in which it is important to maintain a device at a stationary position or to detect relative movement of another component. An example is the use of an exchange wire guide which has a tendency to become displaced as catheters or other instrumentation are advanced or withdrawn over the wire guide. When these procedures are performed using an endoscope, the wire guide can be visualized and therefore, a pattern of markings to determine movement of the wire guide relative to the tip of the endoscope can help in restoring or maintaining proper position of the device. Spiral or helical markings have been used for this purpose; however, such a system cannot permit quantification of the amount of movement, or to make measurements in the body such as the length of a stricture or lesion in a duct or vessel. While scale indicia systems of markings are well known for wire guides and other minimally invasive medical devices, they usually involve fluoroscopic or other methods of measurement that rely on counting dots, bands, etc. to determine relative distances, often a difficult and imprecise method of measurement.
Direct visualization of indicia on the exchange wire guide via an endoscope offers some advantages; however, procedures such as accessing certain treatment sites such as the Papilla of Vater, mucous and other material can obscure the view, making direct measurement impossible. In addition, an exchange wire guide that is useful for measuring strictures for quantifying distance, can be inadequate for discerning movement when the visible area of the wire guide under endoscopy corresponds to gaps between markings. A system that permits endoscopic monitoring of the position of a wire guide to allow reliable and accurate measurement of anatomical structures is needed. Another desirable feature would be to combine the accurate measurement capabilities with a system that allows reliable detection of device movement during a medical procedure to assist in maintaining the device stationary.
The foregoing problems are solved and a technical advance is achieved in an illustrative embodiment of a exchange wire guide used with an endoscope, having multiple types of indicia for indicating position and/or movement within a body of a patient. In present invention, the elongated member, such a wire guide, e.g., a standard solid nitinol core, polymer-coated exchange wire catheter with a tapered or coil wire tip, or a catheter or some other medical device, includes a indicia pattern that is at least partially visible by direct or endoscopic observation. The indicia pattern comprises a first system and a second system of indicia. The first system of indicia includes series of scale reference markings that uniquely identify the particular distance to a fixed reference point on the elongate member, such as the distal tip. These scale references markings can consist of numerals, differently numbered bands, dots, etc., or some other form of unique indicia. The second system of indicia is imprinted on, or incorporated into the elongate member to allow the endoscopist or operator to readily determine whether the elongate member is moving relative to the endoscope into which it situated. The second system of indicia can comprise oblique lines, helical stripes, closely placed marking, or another pattern of indicia that allow one to detect longitudinal shifts in position by viewing the device through an endoscope or monitoring the external portion of the elongate member that extends proximally from the endoscope. Various embodiments of use of the second system of indicia include placement of oblique or closely spaced markings on the distal portion to be viewed by the endoscope, placement of the markings at the proximal portion of the elongate member such that they can be directly viewed externally of the patient to determine relative movement, or to incorporate the helical pattern into the device, e.g., providing a striped wire guide coating or co-extrusion of a bicolor catheter. In the case of the latter, the printed scale reference marker, bands, oblique lines, etc. can be printed over the surface of the device having the helical pattern.
In another aspect of the invention, numeric indicia are placed at selected intervals, e.g., 1 cm, along the distal portion of the wire guide such that they are viewable through an endoscope while the wire guide is positioned within a body passage, such as the gastrointestinal tract. The numerals advantageously provide a simple and accurate system for measurement of anatomical features within the body. The numeric indicia are optionally combined with differing numbered band or other non-numeric indicia at a larger interval, e.g., 5 cm. When the indicia pattern of the present invention is applied to an exchange wire guide, it permits the measurement of anatomical structures when used with an endoscope having an accessory channel for introducing ancillary devices or instrumentation. This obviates the need for separate measuring devices, and makes it especially useful for ERCP (Endoscopic Retrograde Cholangiopancreatography) procedures, when the length of a biliary stricture is to be measured. In one aspect of the invention configured for an ERCP procedure, the endoscope is advanced into the duodenum where the wire guide is then advanced from the distal end of the endoscope into the Papilla of Vater to access the biliary system. Further advancement of the endoscope tip into the common bile duct can often result in the operator""s field of vision being obscured by mucous and/or body fluids. Instead, the tip of the endoscope remains in the duodenum where visibility is superior. To measure the stricture, the wire guide having a radiopaque marker on the distal portion is advanced until it has crossed the stricture. The wire guide tip is made visible by the use of a radiopaque material, either by loading the elastomeric material comprising the tip with a radiopaque material, such as a tungsten or barium powder, e.g., by a method such as that disclosed in U.S. Pat. No. 5,300,048 to Drewes; by addition of a second radiopaque material, such as applying radiopaque bands or shrink tubing, or dipped material; or by making the wire itself radiopaque, such as by placement of a platinum coil over a tapered solid core wire. In one example of how the present invention can be used, the clinician determines the numerical position of the wire guide using an endoscope, then withdraws the wire guide until the radiopaque tip marks the proximal boundary of the stricture. Calculation of the difference between the values observed on the wire guide gives the length of the stricture. This knowledge can be important in subsequent treatment, such as correct sizing of a biliary stent. Once the stricture has been measured, the wire guide can be maintained in place to serve as an exchange wire for introducing other instruments. Optionally, the second system of indicia is useful to the endoscopist in maintaining the wire guide stationary during such an exchange.